1. Field of the Invention
The invention relates to laser manufacturing, in particular to a high-power single emitter semiconductor laser and methods for manufacturing the same.
2. Background
Semiconductor laser is also called laser diode (LD). In 1980s, based on new developments in physics, such as new structures based on quantum well (QW) and strained-layer quantum well (SL-QW), refractive index modulation Bragg transmitters were developed and improved. At the same time, new crystal growth techniques, such as MBE, MOCVD and CBE, were also developed. All of these developments allowed new epitaxial techniques to precisely control crystal growth, enabling one to achieve thickness precision down to the molecular layer level, and to produce high-quality QW and SL-QW materials. Therefore, LDs made from these materials had markedly reduced the current threshold, significantly enhanced conversion efficiency, greatly improved power output, and markedly improved service life time. (With the improvements in the stability, conversion efficiency, and output power, semiconductor lasers are more widely used in laser communication, optical (laser) storage, optical gyroscope, laser printing, distance measurements, radar, etc. The market demand for semiconductor lasers is huge, and the development outlook is expanding.)
At present, although significant improvements have been made in the semiconductor laser technology, due to fast technology advancement, many industries have higher demands for semiconductor laser technology. The main issues with semiconductor lasers are low laser outputs, lower conversion efficiencies, poor performance stabilities, and high costs. These deficiencies greatly limit their application. Performance of semiconductor lasers relates to not only chip, but also heat radiation and packaging of the devices. In order to improve the reliability and stability of semiconductor lasers and to reduce associated production costs, it is necessary to design structures with more reliable packaging and more efficient heat dissipation attributes. This places higher demands on packaging design and manufacture, requiring packaging models to be simple, more efficient and have lower cost characteristics.
Currently, the most widely used high-power single-chip semiconductor lasers use C-mount (see FIG. 1A) and CT-mount (see FIG. 1B) packaging models. These two packaging modes have following flaws:
1) Low efficiency. As the power efficiencies of continuous waves generated by a single emitter semiconductor laser is only 2-3 W, if C-mount and CT-mount packaging models are used, the output power will be reduced due to limited heat dissipation.
2) High cost. CT-mount packaging typically uses copper tungsten (CuW) alloy to make the heat sink for the single emitter semiconductor laser. Because CuW alloy with gold plating is expensive, costs for manufacturing lasers of such packaging models are high.
3). Low heat-dissipation capability. In the C-mount packaging structure, the heat sink is typically located at the vertical side next to the single emitter. In operation, the laser converts about half the operation energy to heat. Because the chip is far from the thermoelectric refrigeration, heat cannot be dissipated quickly, thus resulting in heat concentration, which leads to broadened optical spectrum, wavelength shifts, and shortened product life and reduced reliability of the lasers.
4) Charged heat sink. C-mount and CT-mount packaging models use indium soldering, which causes copper support block to be electrically charged. This reduces safety of the lasers.
5) Low connection reliability. The copper support block of either C-mount or CT-mount packaging model has a single screw hole. This design allows great mechanical freedom and, therefore, results in low connection reliability of the laser.
As can be seen, there are flaws in the currently available single emitter semiconductor lasers and the technique for manufacturing them. Improvements are therefore needed. Manufacturers have tried hard looking for solutions to the above-mentioned problems. However, no suitable design has been developed so far. There is therefore an urgent need to design a new high-power semiconductor laser and to devise a method for making the same.